Body tissues are not ferromagnetic, but ferromagnetic particles can be present as contaminants in the lungs and other organs. Airborne magnetic particles that are inhaled into the lungs become deposited on lung surfaces and are ingested by lung macrophages. These cells defend the respiratory surfaces of the lungs through their phagocytic and migratory capabilities. Strong magnetic fields cause magnetic particles to move and magnetically align. This may be detrimental the function of macrophages containing ferromagnetic particles. Microscopic magnetic particles within cells can also be used as a probe of cell function. We delivered magnetic particles by aerosol inhalation and measured the magnetic fields from macrophages receovered by lung lavage from exposed animals. The particles are tiny permanent magnets, and when aligned, they produce a remanent field which can be measured non-invasively with a sensitive magnetometer. When the particles move and rotate, the remanent field changes. Thus for particles ingested by pulmonary macrophages, cytoplasmic motions rotate particles away from the direction of alignment and cause the remanent field to decrease. In addition, intracellular particles can be twisted by an external field, and the degree to which they rotate in response is a measure of cytosol viscosity. The research proposed will systematically investigate magnetic phenomena in cultured macrophages. The aims will be to: 1) Calibrate the magnetometric technique as a measure of macrophage functional status. 2) Establish procedures for extracting meaningful parameters from the remanent-magnetic-field curves. 3) Use the magnetic signals as a probe for cytoplasmic motion and cytosol rhealogy. 4) Measure the changes in magnetic signals generated when macrophages are exposed to strong external magnetic fields. The results will help establish magnetometry of intracellular ferromagnetic particles as a non-optical method both for monitoring biologic processes within cells and for determining the effects of magnetic fields. Since magnetic particles within intact animals and humans can also be detected, magnetometry may ultimately find application as a non-invasive probe of in situ macrophage function.